By reducing the power consumption of portable electronic devices it is possible to increase the battery life. In the case of audio devices configured to capture and process a voice signal, one technique that has been proposed for reducing power consumption is to use voice activity detection, such that certain processing circuits are only activated when the voice signal is present. At other times, these processing circuits can be powered down, thereby economising energy.
It is important to draw a distinction between voice detection and speech recognition. Voice detection is aimed at generating a Boolean signal indicating whether or not a voice signal is present. Speech recognition is the recognition of one or more words in a voice signal.
Speech recognition is far more complex than voice detection, and thus tends to be significantly more power consuming. Therefore, it has been proposed to only activate speech recognition when a voice signal is detected. However, a difficulty in existing solutions is that the reduction in power consumption is relatively low. On the one hand, if the voice detection algorithm is sufficiently accurate to only activate the speech recognition in cases where voice is really present, this generally means that the voice detection algorithm will be complex and thus have a relatively high power consumption. On the other hand, if the voice detection algorithm has low power consumption, this generally means it will have a relatively high rate of false positive outputs in order to maintain an adequate positive predictive value, meaning that speech recognition will be activated more often than necessary, also leading to relatively high power consumption.